1. Field of the Invention
The present invention relates to boronic ester and acid compounds, their synthesis and uses.
2. Description of Related Art
The synthesis of N-terminal peptidyl boronic ester and acid compounds, in general and of specific compounds, has been described previously (Shenvi et al. U.S. Pat. No. 4,499,082 issued Feb. 12, 1985; Shenvi et al. U.S. Pat. No. 4,537,773 issued Aug. 27, 1985; Siman et al. WO 91/13904 published Sep. 19, 1991; Kettner et al., J. Biol. Chem. 259(24): 15106-15114 (1984). These compounds have been shown to be inhibitors of certain proteolytic enzymes (Shenvi et al. U.S. Pat. No. 4,499,082 issued Feb. 12, 1985; Shenvi et al. U.S. Pat. No. 4,537,773; Siman et al. WO 91/13904 published Sep. 19, 1991; Kettner at al., J. Biol. Chem. 259(24):15106-15114 (1984). A class of N-terminal tri-peptide boronic ester and acid compounds has been shown to inhibit the growth of cancer cells (Kinder et al. U.S. Pat. No. 5,106,948 issued Apr. 21, 1992). A broad class of N-terminal tri-peptide boronic ester and acid compounds and analogs thereof has been shown to inhibit renin (Kleeman et al. U.S. Pat. No. 5,169,841 issued Dec. 8, 1992).
In the cell, there is a soluble proteolytic pathway that requires ATP and involves covalent conjugation of the cellular proteins with the small polypeptide ubiquitin (xe2x80x9cUbxe2x80x9d) (Hershko et al., A. Rev. Biochem. 61:761-807 (1992); Rechsteiner et al., A. Rev. Cell. Biol. 3:1-30(1987)). Thereafter, the conjugated proteins are hydrolyzed by a 26S proteolytic complex containing a 20S degradative particle called the proteasome (Goldberg, Eur. J. Biochem. 203:9-23 (1992); Goldberg et al., Nature 357:375-379 (1992)). This multicomponent system is known to catalyze the selective degradation of highly abnormal proteins and short-lived regulatory proteins.
The 20S proteasome is composed of about 15 distinct 20-30 kDa subunits. It contains three different peptidase activities that cleave specifically on the carboxyl side of the hydrophobic, basic, and acidic amino acids (Goldberg et al., Nature 357:375-379 (1992); Goldberg, Eur. J. Biochem. 203:9-23 (1992); Orlowski, Biochemistry 29:10289 (1990); Rivett et al., Archs. Biochem. Biophys. 218:1 (1989); Rivett et al., J. Biol. Chem. 264:12,215-12,219 (1989); Tanaka et al., New Biol. 4:1-11 (1992)). These peptidase activities are referred to as the chymotrypsin-like activity, the trypsin-like activity, and the peptidylglutamyl hydrolyzing activity, respectively.
Various inhibitors of the peptidase activities of the proteasome have been reported (Dick et al., Biochemistry 30:2725-2734 (1991); Goldberg et al., Nature 357:375-379 (1992); Goldberg, Eur. J. Biochem. 203:9-23 (1992); Orlowski, Biochemistry 29:10289 (1990); Rivett et al., Archs. Biochem. Biophys. 218:1 (1989); Rivett et al., J. Biol. Chem. 264:12,215-12,219(1989); Tanaka et al., New Biol. 4:1-11 (1992); Murakami et al., Proc. Natl. Acad. Sci. U.S.A. 83:7588-7592 (1986); Li et al., Biochemistry 30:9709-9715 (1991); Goldberg, Eur. J. Biochem. 203:9-23 (1992); Aoyagi et al., Proteases and Biological Control, Cold Spring Harbor Laboratory Press (1975), pp. 429-454.
Stein et al., U.S. patent application Ser. No. 08/212,909 filed Mar. 15, 1994, describe the use of peptide aldehydes to 1) reduce the rate of loss of muscle mass in an animal by contacting cells of the muscle with a peptide aldelyde proteasome inhibitor, 2) reduce the rate of intracellular protein breakdown in an animal by contacting cells of the animal with a peptide aldehyde proteasome inhibitor, and 3) reduce the rate of degradation of p53 protein in an animal by administering to the animal a peptide aldehyde proteasome inhibitor.
Palombella et al., PCT application serial number PCT/US95/03315, filed Mar. 17, 1995, describe the use of peptide aldehydes to reduce the cellular content and activity of NF-xcexaB in an animal by contacting cells of the animal with a peptide aldehyde inhibitor of proteasome function or ubiquitin conjugation.
The transcription factor NF-xcexaB and other members of the rel family of protein complexes play a central role in the regulation of a remarkably diverse set of genes involved in the immune and inflammatory responses (Grilli et al., International Review of Cytology 143:1-62 (1993)). NF-xcexaB exists in an inactive form in the cytoplasm complexed with an inhibitor protein, IxcexaB. In order for the NF-xcexaB to become active and perform its function, it must enter the cell nucleus. It cannot do this, however, until the IxcexaB portion of the complex is removed, a process referred to by those skilled in the art as the activation of, or processing of, NF-xcexaB. In some diseases, the normal performance of its function by the NF-xcexaB can be detrimental to the health of the patient. For example, NF-xcexaB is essential for the expression of the human immunodeficiency virus (HIV). Accordingly, a process that would prevent the activation of the NF-xcexaB in patients suffering from such diseases could be therapeutically beneficial.
Goldberg and Rock, WO 94/17816, filed Jan. 27, 1994, describe the use of proteasome inhibitors to inhibit MHC-I antigen presentation. The ubiquitination/proteolysis pathway is shown to be involved in the processing of internalized cellular or viral antigens into antigenic peptides that bind to MHC-I molecules on an antigen presenting cell. Accordingly, inhibitors of this pathway would be useful for the treatment of diseases that result from undesired response to antigen presentation, including autoimmune diseases and transplant rejection.
Cyclins are proteins that are involved in cell cycle control in eukaryotes. Cyclins presumably act by regulating the activity of protein kinases, and their programmed degradation at specific stages of the cell cycle is required for the transition from one stage to the next. Experiments utilizing modified ubiquitin (Glotzer et al., Nature 349:132-138 (1991); Hershko et al., J. Biol. Chem. 266:376 (1991)) have established that the ubiquitination/proteolysis pathway is involved in cyclin degradation. Accordingly, compounds that inhibit this pathway would cause cell cycle arrest and would be useful in the treatment of cancer, psoriasis, restenosis, and other cell proliferative diseases.
The present invention provides previously unknown peptidyl boronic acid ester and acid compounds. The present invention also provides methods of using amino acid or peptidyl boronic ester and acid compounds, in general, as inhibitors of proteasome function.
In a first embodiment, the present invention provides novel boronic acid and ester compounds having formula (1a) or (2a), as set forth below.
An additional aspect of the present invention is related to the discovery that amino acid and peptidyl boronic acids and esters, in general, are potent and highly selective proteasome inhibitors and can be employed to inhibit proteasome function. Inhibition of proteasome function has a number of practical therapeutic and prophylactic applications.
In a second embodiment, the present invention provides a method for reducing the rate of muscle protein degradation in a cell comprising contacting said cell with a proteasome inhibitor having formula (1b) or (2b) as defined below. This aspect of the present invention finds practical utility in inhibiting (reducing or preventing) the accelerated breakdown of muscle proteins that accompanies various physiological and pathological states and is responsible to a large extent for the loss of muscle mass (atrophy) that follows nerve injury, fasting, fever, acidosis, and certain endocrinopathies.
In a third embodiment, the present invention provides a method for reducing the activity of NF-xcexaB in a cell comprising contacting the cell with a proteasome inhibitor of the formula (1b) or (2b), as set forth below. The inhibitors employed in the practice of the present invention are capable of preventing this activation. Thus, blocking NF-xcexaB activity is contemplated as possessing important practical application in various areas of medicine, e.g., inflammation, sepsis, AIDS, and the like.
In a fourth embodiment, the present invention provides a method of reducing the rate of degradation of p53 protein in a cell comprising administering to the cell a proteasome inhibitor of the formula (1b) or (2b), as set forth below.
In a fifth embodiment, the present invention provides a method for inhibiting cyclin degradation in a cell comprising contacting said cells with a proteasome inhibitor of the formula (1b) or (2b), as set forth below. Inhibiting cyclin degradation is contemplated as possessing important practical application in treating cell proliferative diseases, such as cancer, restenosis and psoriasis.
In a sixth embodiment, the present invention provides a method for inhibiting the growth of a cancer cell, comprising contacting said cell with a proteasome inhibitor of the formula (1a) or (2a), as set forth below.
In a seventh embodiment, the present invention provides a method for inhibiting antigen presentation in a cell comprising administering to the cell a proteasome inhibitor of the formula (1b) or (2b), as set forth below.
In an eighth embodiment, the present invention provides a method for inhibiting inducible NF-xcexaB dependent cell adhesion in an animal comprising administering to said animal a proteasome inhibitor of the formula (1b) or (2b), as set forth below.
In a ninth embodiment, the present invention provides a method for inhibiting HIV replication in an animal comprising administering to said animal a proteasome inhibitor of the formula (1b) or (2b), as set forth below.
In a tenth embodiment, the present invention provides an approach for inhibiting cytolytic immune responses. The proteasome inhibitors of formula (1b) or (2b) can be used to inhibit the processing of internalized cellular or viral antigens into antigenic peptides that bind to MHC-I molecules in an animal, and are therefore useful for treating autoimmune diseases and preventing rejection of foreign tissues, such as transplanted organs or grafts.
In an eleventh embodiment, the present invention provides pharmaceutical compositions that comprise compounds of formula (1a), (1b), (2a) or (2b) in an amount effective to inhibit proteasome function in a mammal, and a pharmaceutically acceptable carrier or diluent.